The present invention concerns a plasticizing unit for a molding machine, and a molding machine with such a plasticizing unit.
Depending on the material a tempering of the plasticizing cylinder in the form of a cooling or a heating can be necessary.
In the case of generic molding machines, the material to be plasticized (p. e. plastic granulate or powder, metal powder, etc.) is subjected to shear forces which is accompanied with heat development. This can have the disadvantageous effect that the material to be plasticized can partly melt or stick together in the area of the filling opening and in the feeding zone, whereby the grain size changes in the case of a granular material, which influences the feeding behavior in an unpredictable way. It can even lead to a blocking of the filling opening by the melted material.
It is already known to provide the filling opening with an active tempering device and to additionally arrange a thermal separating device between the feeding zone and the filling opening. Such a plasticizing unit is for example disclosed in the WO 2008/000613 A1.
It is disadvantageous that with the active tempering device shown in the above mentioned document, the temperature of the filling opening can only vary in a very small range.
Generic plasticizing units for a molding machine with a plasticizing cylinder can comprise a user-operable adjusting device for adjusting a position of a nozzle of the plasticizing cylinder. Here, the problem exists that due to an operating error of the adjusting device, unacceptably high mechanical tensions can occur in the plasticizing cylinder, which can be particularly problematic in combination with a thermal separating device.